The present invention relates to a method of dialyzing blood using an artificial kidney, including a flat membrane system wherein blood flows between semipermeable membranes of multi-plate form and a dialyzing liquid comes into contact with blood through the dialyzing membrane so as to clarify the blood, or a hollow pipe system wherein blood is clarified during circulation in a number of hollow pipes, more particularly it relates to a blood dialyzing method which enables one to remove toxins, such as harmful substances which are removed by the kidney, such as methyl guanidine, guanidinosuccinic acid contained within blood, which cannot be easily removed by a conventional dialyzing membrane.
In general, artificial kidneys perform the functions of bringing blood into contact with a dialyzing liquid through a dialyzing membrane, removing harmful substances, such as water, urea, uric acid, creatinine, electrolytic substances including sodium ions and magnesium ions, sulfate radical, and phosphate radical contained within the blood, and adding filling-up substances from the dialyzing liquid, such as calcium ions, grapesugar, and water, to the blood.
At present, an artificial kidney functions to remove waste products; and "toxins" generally means such harmful substances as cannot be easily removed by a dialyzing membrane.
Toxins are organic substances of higher or medium molecular weight (The medium molecular weight ranges from 300 to 3000.). Toxins have such dimension that they cannot pass through small holes having a diameter of 20.about.30 A on a dialyzing membrane which is thought optimum in its function at present. If the diameter of small holes on the dialyzing membrane is enlarged, other useful substances are also removed causing a bad effect on the blood. Toxins include, for example, methyl guanidine or guanidino-succinic acid having large viscosity. Blood contains useful sobstances such as various amino acids, vitamines, and hormones. These substances are as large as, but not as, viscous as toxins.
In a conventional artificial kidney using a dialyzing liquid, there is a flat membrane system wherein blood is clarified during its flow between semipermeable membranes of a multi-plate form and a hollow pipe system wherein the blood is clarified during circulation in a number of hollow pipes. Such systems can dialyze substances, for example, water, creatinine, sodium ions, potassium ions, sulfate radical, and phosphate radical, which are smaller than the inner diameter of the discharge hole on the dialyzing membrane, however, they cannot remove said toxins which are larger than the discharge hole diameter.
In recent years, methods of removing these toxins are being investigated. In one method, for example, blood-plasma which contains toxins and also useful substances such as hormones is separated, in turn said contained substances are adsorbed in activated carbon. This method, however, has disadvantage in that useful substances for human bodies, such as hormones, may also be removed.
In another method, blood-plasma which contains toxins together with useful substances such as hormones and vitamins, is separated in a dialyzing liquid by means of a filtering process, in turn, substitutive plasma is supplied. Such substitutive plasma is not the same as proper blood-plasma in all properties. Therefore, the method is not sufficient to moderate the condition of a patient, and it must be further improved at all points.